meta_programming.py

class MyClass(object):
    pass

# is identical to

# type(name, bases, dct)
# - name is a string giving the name of the class to be constructed
# - bases is a tuple giving the parent classes of the class to be constructed
# - dct is a dictionary of the attributes and methods of the class to be constructed
MyClass = type('MyClass', (), {})

# Example: Registry
class DBInterfaceMeta(type):
    # we use __init__ rather than __new__ here because we want
    # to modify attributes of the class *after* they have been
    # created
    def __init__(cls, name, bases, dct):
        if not hasattr(cls, 'registry'):
            # this is the base class.  Create an empty registry
            cls.registry = {}
        else:
            # this is a derived class.  Add cls to the registry
            interface_id = name.lower()
            cls.registry[interface_id] = cls
            
        super(DBInterfaceMeta, cls).__init__(name, bases, dct)

class DBInterface(object):
    __metaclass__ = DBInterfaceMeta
    
print(DBInterface.registry)
# {}

class FirstInterface(DBInterface):
    pass

class SecondInterface(DBInterface):
    pass

class SecondInterfaceModified(SecondInterface):
    pass

print(DBInterface.registry)
# {'firstinterface': <class '__main__.FirstInterface'>, 'secondinterface': <class '__main__.SecondInterface'>, 'secondinterfacemodified': <class '__main__.SecondInterfaceModified'>}